The present invention relates generally to a disc drive system, and more particularly to a ramp assembly method and apparatus for loading and unloading an actuator arm in a disc drive.
Disc drive systems read and write information stored on concentric circular tracks on memory discs. Information or data is stored on the surface of the memory discs via a read/write transducer, or head. The data is divided or grouped together in tracks. The read/write heads, located on both sides of the memory disc, read and write information on the memory discs when they are accurately positioned over one of the designated or target tracks on the surface of the memory disc. As the memory disc spins and the read/write head is accurately positioned above a target track, the read/write head can store data onto a track by writing onto the memory disc in a particular manner. Similarly, reading data on a memory disc is accomplished by positioning the read/write head above a target track and reading the stored material on the memory disc. To write on or read from different tracks, the read/write head is moved radially across the concentric tracks to the target track.
Typical disc drives have a plurality of memory discs spaced apart and rotating about a common spindle. Because of the importance of positioning the read/write head substantially parallel to the memory disc surface, a head gimbal assembly mounted on an actuator arm. The read/write head is found at the distal end of the actuator arm on the gimbal assembly. The flexure and head gimbal assembly allow the read/write head to gimbal for pitch and roll to follow fluctuations in the imperfect memory disc surface but restrict motion in the radial and circumferential directions of the memory disc. The proximal end of the actuator arm is coupled to a pivot assembly. The pivot assembly is in turn connected to a motor system. As the disc drive system sends control signals to the motor, the motor rotates, thereby displacing the actuator arm supporting the read/write head across the memory disc in a radial direction to the target track. The control signals indicate to the motor the magnitude and direction of the displacement.
In many disc drives, ramp assemblies are utilized to prevent actuator arm assembly and specifically the transducer it supports from contacting the discs when the transducer is in the park or non-operating position. In the park mode, the actuator arm assembly is moved to the perimeter of the disc where a ramp assembly is located. Preferably, the ramp is located adjacent the edge of the disc, so that no data storage space on the disc is lost. Alternatively, the ramp assembly is located at the perimeter of the disc over an unrecordable region of the disc. The head cannot read or write data when the actuator arm is parked, on the ramp. The ramp assembly displaces the actuator arm assembly in a vertical direction to prevent it from touching the disc even in the event of a significant shock.
In many prior art designs, the loading (moving the actuator arm into position to fly over the disc) and unloading (moving the actuator arm onto the ramp assembly) steps generate debris as a portion of the actuator arm (e.g., the flexure) slides or rubs against the ramp surface. Many ramp assemblies are made of plastic whereas the flexure is made of metal. Metal (e.g., stainless steel) flexures will scrape away at any surface that it rubs against. Metal flexures rubbing against plastic ramps generate a substantial amount of debris which are detrimental to sensitive parts of the disc drive system. These metal-on-plastic assemblies generate high friction and thus, are not an optimum low-friction combination for minimizing actuator torque required to load and unload the actuator arm. Additionally, smaller disc drive systems (e.g., 1.8-inch or smaller) require very small, thin, and robust ramp parts. Plastic ramps are not structurally robust.
Other combinations of flexure and ramp assembly parts such as metal-on-metal generate excessive friction and wear. The debris resulting from such wear is undesirable for these sensitive disc drives. The predominant solution in the industry has been to avoid using ramps altogether to eliminate debris. Some manufacturers utilize ramps and live with the risk of high-wear (and thus, high-debris) disc drive systems.
An object of the invention is to minimize the generation of debris due to a ramp assembly in a disc drive system.
Another object of the invention is to substantially prevent debris from contacting sensitive disc drive parts.
A further object of the invention is to minimize friction to minimize actuator torque required to load and unload the actuator arm.
The foregoing and other objects are achieved by a disc drive system utilizing a ramp and actuator arm assembly where both the ramp surface and the contacting portion of actuator arm surface are coated with a hard, low-friction polymer such as a Teflon (polytetrafluoroethylene or tetrafluoroethylene) and molybdenum-disulfide loaded polyamide. Additionally, applying a lubricant to the stationary part confines flying debris within the lubricant. Usually, the stationary part is the ramp assembly. The coating-on-coating between the two rubbing surfaces minimizes debris and friction.